sysctl: share unsigned long const values

Provide a way to share unsigned long values.  This will allow others to
not have to re-invent these values.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Luis Chamberlain <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Amir Goldstein <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: Antti Palosaari <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Benjamin LaHaise <[email protected]>
Cc: Clemens Ladisch <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Douglas Gilbert <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Iurii Zaikin <[email protected]>
Cc: James E.J. Bottomley <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: John Ogness <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Joseph Qi <[email protected]>
Cc: Julia Lawall <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Lukas Middendorf <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Martin K. Petersen <[email protected]>
Cc: Paul Turner <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Phillip Potter <[email protected]>
Cc: Qing Wang <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: Sebastian Reichel <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Stephen Kitt <[email protected]>
Cc: Steven Rostedt (VMware) <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Tetsuo Handa <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: Xiaoming Ni <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/proc/proc_sysctl.c

@@ -29,6 +29,9 @@ static const struct inode_operations proc_sys_dir_operations;
 const int sysctl_vals[] = { -1, 0, 1, 2, 4, 100, 200, 1000, 3000, INT_MAX };
 EXPORT_SYMBOL(sysctl_vals);
 
+const unsigned long sysctl_long_vals[] = { 0, 1, LONG_MAX };
+EXPORT_SYMBOL_GPL(sysctl_long_vals);
+
 /* Support for permanently empty directories */
 
 struct ctl_table sysctl_mount_point[] = {

include/linux/sysctl.h

@@ -51,6 +51,12 @@ struct ctl_dir;
 
 extern const int sysctl_vals[];
 
+#define SYSCTL_LONG_ZERO	((void *)&sysctl_long_vals[0])
+#define SYSCTL_LONG_ONE		((void *)&sysctl_long_vals[1])
+#define SYSCTL_LONG_MAX		((void *)&sysctl_long_vals[2])
+
+extern const unsigned long sysctl_long_vals[];
+
 typedef int proc_handler(struct ctl_table *ctl, int write, void *buffer,
 		size_t *lenp, loff_t *ppos);
 

kernel/sysctl.c

@@ -100,9 +100,6 @@
 
 /* Constants used for minimum and  maximum */
 
-static const unsigned long zero_ul;
-static const unsigned long one_ul = 1;
-static const unsigned long long_max = LONG_MAX;
 #ifdef CONFIG_PRINTK
 static const int ten_thousand = 10000;
 #endif
@@ -2513,7 +2510,7 @@ static struct ctl_table vm_table[] = {
 		.maxlen		= sizeof(dirty_background_bytes),
 		.mode		= 0644,
 		.proc_handler	= dirty_background_bytes_handler,
-		.extra1		= (void *)&one_ul,
+		.extra1		= SYSCTL_LONG_ONE,
 	},
 	{
 		.procname	= "dirty_ratio",
@@ -2931,8 +2928,8 @@ static struct ctl_table fs_table[] = {
 		.maxlen		= sizeof(files_stat.max_files),
 		.mode		= 0644,
 		.proc_handler	= proc_doulongvec_minmax,
-		.extra1		= (void *)&zero_ul,
-		.extra2		= (void *)&long_max,
+		.extra1		= SYSCTL_LONG_ZERO,
+		.extra2		= SYSCTL_LONG_MAX,
 	},
 	{
 		.procname	= "nr_open",